Various contaminants generated in a semiconductor device manufacturing process adhere to a surface of a target substrate such as a semiconductor wafer (hereinafter, referred to as “wafer”), and in order to remove the contaminants, there has been performed a cleaning process for cleaning the surface of the wafer by using a multiple number of cleaning solutions.
By way of example, in a substrate processing apparatus which performs a batch type cleaning process, there has been widely employed a cleaning method in which for example, several tens of wafers are immersed in sequence in a cleaning solution such as a chemical solution or a rinse solution in a processing tank. After the cleaning process, the wafers are picked up from the cleaning solution and then a drying gas including vapor of a solvent such as IPA (isopropyl alcohol) is injected to remove a liquid (for example, water) from the surface of the wafer and prevent generation of water marks.
In the semiconductor device manufacturing process, a stacked structure is formed on the surface of the wafer by photolithography, and, thus, a pattern made of materials including an organic material, such as a resist film, is formed on the surface of the cleaning target wafer. Recently, as a wiring structure in a semiconductor device becomes miniaturized, such a pattern also becomes miniaturized, so that its mechanical strength or chemical resistance may be decreased as compared with a conventional one.
If the drying gas including the solvent such as IPA is brought into contact with such a resist film, for example, a trench pattern 80 shown in FIG. 13A may be deformed into a taper pattern 81, a collapsed pattern 82, a disappeared pattern 83 or dissolved pattern 84 as depicted in FIG. 13B. In a manufacturing process of such a miniaturized semiconductor device, such a deformation may be a big problem in improving product yield.
In the semiconductor device manufacturing process, a wafer is transferred while its peripheral area, on which a semiconductor device is not formed, is held or grasped by a transfer arm or tweezers. For this reason, more particles adhere to the peripheral area of the wafer than its central area and non-removed particles may remain on the peripheral area even after a cleaning process.
Meanwhile, in the batch type cleaning process, a wafer may be immersed in the cleaning solution in a longitudinal direction and picked up from the cleaning solution in the longitudinal direction and then dried. In this case, if the wafer is brought into contact with IPA vapor, the IPA may be adsorbed to water on the surface of the wafer and a liquid film mixed with the water and the IPA may be formed and may flow down the surface of the wafer by a decrease in surface tension or weight of the liquid film. The present inventors have found that relatively many particles remaining in a peripheral area of the wafer flow toward a central area of the wafer along the flow of the liquid film and contaminate an area where the semiconductor device is formed.
In Patent Document 1, it is disclosed that vapor of a drying fluid such as IPA is supplied in advance to an upper region of a cleaning solution such as pure water in which a wafer is immersed and an atmosphere around the wafer is slowly and directly changed from the cleaning solution to the IPA vapor so as to dry the wafer. However, even in this case, if the IPA as the drying fluid is supplied in large quantities, there is the same problem as the above-described drying method in which the wafer is picked up and then the IPA vapor is supplied to the wafer. By way of example, a liquid film of the IPA condensed on the surface of the wafer may flow down the surface of the wafer together with particles and may contaminate an area where a semiconductor device is formed.
Patent Document 1: Japanese Patent No. H06-103686 (see claim 1 and Lines 39 to 43 of the left column of page 4)